Technical Field
This technology relates to lightweight, breathable, non-woven fibrous materials and composite articles incorporating the same.
Description of the Related Art
High performance fibrous composites formed from high strength fibers are well known in various industries. High strength fibers conventionally used include polyolefin fibers, such as extended chain polyethylene fibers, and aramid fibers, such as para- and meta-aramid fibers. For many applications, the fibers may be used in a woven or knitted fabric, while for other applications the fibers may be formed into non-woven fabrics. No matter the industry, there is a constant desire for fabrics that are lighter weight while still strong and resistant to degradation and damage. In the armor industry, the most desirable fibrous composite articles are those having the greatest ballistic resistance possible at the lightest weight possible, while other optional features such as abrasion resistance or environmental resistance are typically of secondary importance. In non-armor industries, such as textile industries that fabricate wearable textile articles such as sports apparel and footwear, as well as non-wearable textile articles such as tents, properties such as environmental resistance and breathability are equally as important as high strength and light weight.
In this regard, it is desirable for fibrous composites that are designed to have good environmental resistance to be breathable so that water vapor can pass through the fabric while blocking passage of liquids, as well as to prevent condensation, user perspiration, etc., from building up on or underneath the fabric. Conventionally, environmentally resistant non-armor textile products have been fabricated as multilayer structures incorporating woven fabrics as reinforcing components members, particularly fabrics woven from very low denier fibers (i.e., 1 denier or less) having relatively low tenacities (i.e., 10 g/denier or less), or non-woven felted fabrics, which felted fabric are formed from randomly laid fibers and have a degree of porosity that allows vapors to pass therethrough while blocking liquids. Each of these types of breathable structures has disadvantages. Breathable woven fabrics, for example, do not utilize the full tensile strength of the fibers due to the inherent crimping of fibers due to the weaving process. Such fiber crimp also reduces the ability of the system to stay in tension, which is particularly problematic when high strength is of primary importance. See, for example, U.S. Pat. No. 8,193,105 which teaches a breathable waterproof fabric formed to resist allergen transmission. The fabrics are woven from low tenacity polyester or natural fibers to achieve a porous, breathable structure having a pore size of less than one micron. U.S. Pat. No. 7,682,994 teaches a woven fabric that is permeable to water vapor and impermeable to liquid water. The fabric comprises a combination of low tenacity hydrophobic fibers and low tenacity hydrophilic wicking yarns. Similarly, breathable felted fabrics are unable to utilize the full tensile strength of the fibers due to the randomized orientation of the fibers. In this regard, greatest strength of a fiber is along its longitudinal axis, and therefore the physical strength of a felted fabric varies depending on the direction of an applied load. See, for example, U.S. Pat. No. 8,328,968 which teaches a microporous composite sheet material comprising spun bonded, randomly disposed polyester fibers that are bonded together to form a porous, non-woven felt. This material is breathable but suffers from inadequate tensile strength.
It is therefore recognized that to maximize the strength of reinforced breathable materials, reinforcing elements that are straight and not crimped should be utilized. One such approach is disclosed in U.S. pre-grant publication 2015/0282544 which teaches multilayered, breathable, waterproof textile materials. Fibers in a first non-woven layer form an angle of approximately 90° with respect to the fibers in a second non-woven layer. Each fiber of each fabric layer is embedded within a matrix material and the layers are compacted such that the fibers in each layer are laterally married to each other. In some embodiments, this matrix material is a non-hydrophilic material that is applied in sufficiently thin concentrations to allow gaps to form between the fibers, which gaps are then filled with a hydrophilic material. In other embodiments, the matrix material is a hydrophilic material that fully fills any spaces between adjacent fibers. The fabric layers are then laminated between an outer hydrophobic polymer layer and a polyurethane inner membrane. While these composite materials are described as having good breathability, their utility is limited by the need to have adjacent fibers laterally married with each other for proper structural stability (as is described in their commonly-owned U.S. Pat. No. 5,333,568 which is incorporated by reference into their disclosure), which results in significantly greater fiber content and fabric weight relative to a composite that does not require such lateral marriage of fibers. Another approach is disclosed in U.S. Pat. No. 8,784,968 which teaches waterproof breathable materials that are reinforced with non-woven fabrics wherein areas between the fibers are either free from a gas permeability blocking polymer or contain a permeable W/B adhesive or film which allows gas breathability while preventing or inhibiting the flow of fluids. As described therein, all of the fibers in their materials are enclosed by an adhesive that forms a cover over each individual fiber, forming these elongate bodies into a conventionally known “core-sheath” structure. As shown in their FIGS. 1-3, 5 and 6, such a cover (i.e., the sheath) substantially increases the size and volume occupied by the fiber (i.e., the core) within the composite, as well as increases the distance between adjacent fibers, both laterally adjacent as well as between overlying-underlying fibers within adjacent planes in a multi-layer stack. This type of structure has limited utility because the resin content is greater than the actual content of the high strength fibers, which limits the physical strength of the resulting composite articles and makes the composite more susceptible to degradation during use. Accordingly, there remains a need in the art for textile articles having superior physical strength, light weight and breathability, which may also be produced with improved efficiency and at a lower cost. The present disclosure provides a solution to this need.